Guild Wars 2 – Roadblock

Head into the instance found in the central part of the Wayfarer's Foothills. Just a little ways in you will find the Gear Warband waiting for you. Approach them to trigger a cinematic that will set the story in motion:
Mangonel: “Welcome to the party, Slayer. If those dredge hurt our Chugger, I'm gonna hit them so hard their children will be born bruised!”
Ballista: “Pay attention you rejects! We've planted a mine in the road. It's not armed yet, because I don't want some random idiot setting it off.”
Slayer: “A mine? I thought you wanted to recover the vehicle, not blow it up.”
Ballista: “Quiet, you. This is front line Iron Legion equipment, not asuran crystal-magic rainbow trash. It might get a dent, but the dredge won't get off that easy.”
Mangonel: “You like shredded mole meat, Slayer? Ha! Don't worry, we'll hose the chugger off before we drive it home.”
Ballista: “Gear Warband! Take positions in the tree line. Not you, Slayer. I got a special job for you. Go in, arm the mine, then fall back. When it detonates under the vehicle, you lead the charge! Ready? Good. Now get moving!”

Head to the North and through the wreckage to find the mine. Interact with it and then fall back once it is armed to the East. Wait with the Warband until you hear the bang or the order to move. A cutscene runs to show the dredge coming in on the Chugger. Once it is over it is time to get to fighting once again.

This first round is simple. You have only 4 or so dredge to deal with and a whole warband ready for a fight. Head in with the Charr and help them clear out the surviving dredge around their tank. Another cutscene will run once they have cleared away the dredge. More are coming in and they are not going to be as easy to tackle as the first round. This time you are facing off against 7 dredge with the warband's aid. After them will come another sizable wave for you to fight your way through. Just keep it up through the next 2 waves.

At this point the dredge get more serious. You will see them emerge with their transports and a large number of dredge will start to emerge. Quickly head to the transports and start smashing them up. It takes time but it is very possible. Just watch out for the Dredge Minign Staff. This is your main target and you want to destroy it as quickly as possible. When the dust has settled and all the dredge are dead on the ground you are treated to another cinematic:
Mangonel: “All clear. Now that was a real kick in the arse! I didn't think dredge had that kind of fight in 'em.”
Ballista: “Stop crowing and sweep the area for survivors. We don't want any more surprises. All right, Slayer. It's ours again and you're clear. But if you really want to square things, I've got one more job for you.”
Slayer: “name it. If I can repay you with interest, so much the better.”
Ballista: “We're ordered to find the Ascalonian ghosts that are attacking caravans near Grendich Ruins and give them a taste of our munitions.”
Slayer: “It'd be my pleasure. I never did get a chance to fire that cannon.”

That completes this part of the quest. Choose your reward and move onto the next part of it, “The Machine In Action.”